linux-kernel - Re: [PATCH net-next V2 1/3] vhost: better detection of available buffers

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Message-ID: <20170103130830.GA14707@stefanha-x1.localdomain>
Date:   Tue, 3 Jan 2017 13:08:30 +0000
From:   Stefan Hajnoczi <stefanha@...il.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next V2 1/3] vhost: better detection of available
 buffers

On Wed, Dec 28, 2016 at 04:09:29PM +0800, Jason Wang wrote:
> This patch tries to do several tweaks on vhost_vq_avail_empty() for a
> better performance:
> 
> - check cached avail index first which could avoid userspace memory access.
> - using unlikely() for the failure of userspace access
> - check vq->last_avail_idx instead of cached avail index as the last
>   step.
> 
> This patch is need for batching supports which needs to peek whether
> or not there's still available buffers in the ring.
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/vhost/vhost.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@...hat.com>

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